In recent years, ionic liquids have been extensively evaluated as environmental-friendly or “green” alternatives to conventional organic solvents for a broad range of organic synthetic applications. Ionic liquids offer some unique characteristics that distinguish them from conventional organic solvents, such as no effective vapor pressure, a broad liquid range, high polarity and charge density, hydrophobic or hydrophilic characteristics, and unique solvating properties.
Additionally, ionic liquids have been shown to be effective in applications where water-based chemistry can be problematic (for example, applications involving proton transfer or nucleophilicity), or in applications where certain coordination chemistry could have a damaging effect on the substrates involved.
Recently, ionic liquids and ionic liquid cocktails have found applications in consumer products (such as home care, air care, surface cleaning, laundry and fabric care formulations) and industrial products. Exemplary ionic liquid containing consumer products are described in US 2004/0077519A1. Moreover, compositions containing ionic liquids composed of an ion active and an ionic liquid forming counterion are described in U.S. patent application Ser. No. 60/624,128.
Some ingredients used in consumer products are supplied by the manufacturers in a highly concentrated form. In some cases, up to 70-90 weight % of the concentrate is the active ingredient. The concentrates may use organic solvents, such as isopropanol or ethanol, and sometimes a minor amount (up to 10%) of water and/or surfactants may be used. In the process of making consumer products, the active concentrates are diluted with water and optionally alcohols. The resulting products are distributed to the retailers and/or consumers. Dispersibility and viscosity characteristics of these active concentrates can pose serious problems for the processors. Surfactant active materials are available as aqueous dispersions only at relatively low concentrations. It is generally not possible to prepare such aqueous dispersions with more than about 30% of the active materials without encountering intractable problems of product viscosity and storage stability. Such problems are manifested in phase separated and/or non-pourable products, inadequate dispersion and/or poor dissolving characteristics under normal use conditions.
It is desirable to take advantage of the various unique characteristics of the ionic liquid to address these problems.
Conventionally, ionic liquids are prepared by mixing the raw materials in chlorinated solvents, such as methylene chloride or carbon tetrachloride. To recover the ionic liquid, a vacuum is applied to evaporate the chlorinated solvents. It is not practical to use this conventional process for industrial production for several reasons. Vacuum evaporation is slow and energy intensive. Special measures must be employed in order to meet the regulatory requirements for handling these solvents. It is difficult to remove the final traces of the chlorinated solvents from the ionic liquid, thus, rendering the resulting ionic liquids unsuitable for many consumer product applications.
Therefore, it is desirable to have a batch, or, preferably, a continuous process for making ionic liquid active concentrates in an aqueous carrier. It is also desirable that the continuous process makes aqueous concentrates with high active contents. Specifically, it is desirable to have aqueous ionic liquid active concentrates having proper viscosity and dispersibility so that the concentrates can be easily processed into consumer products. Additionally, it is desirable that the ionic liquid active concentrates have phase or dispersion stability suitable for shipping and storage.